Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
Our recommendations for commercial garlic production most commonly are to plant in the fall, overwinter, and then harvest in the late spring or early summer. Experience has shown that spring planted garlic is often lower yielding and may not divide into cloves but produce only solid bulbs. However, there are growers that in our region that have had success with late winter planted garlic that produced good yields. The following are some recommendations for late winter planted garlic.
Garlic needs a cold period of 3-6 weeks below 40oF to produce normal bulbs. The longer the cold period the better. Hardneck types such as the popular Porcelain variety ‘Music’ need more cold than the softneck types such as ‘Polish White’. Obtain cold treated garlic bulbs or treat bulbs by placing in a cold box at those temperatures for a minimum of 2 weeks. When you get your bulbs separate into cloves and only plant the largest, rounded (or plump) ones.
Only the largest cloves should be planted.
Prepare your soil as early as it can be tilled, add necessary lime, phosphorus, and potassium (150 lbs./a of each) and 125 lbs./a of N as Ammonium Sulfate. Sites that warm up quickly or sites with every row rye windbreaks that will protect against wind (once elongated) are best. Warm soils will promote early growth.
Lay black plastic mulch on raised beds with 2 drip lines. Plant cloves pointed side up, through the mulch at regular garlic spacing (3-4 rows per bed, 6-8 inches between cloves) no deeper than 2 inches. Plant in late February or early March using the largest cold treated cloves. Add an additional 25 lbs./a N once garlic is 6 inches tall through the drip system and irrigate regularly. The goal is to get as much top growth as possible before bulbing is initiated in April.
Following these guidelines, a spring crop of garlic can be successful.
Late winter planted garlic is best planted on raised beds with black plastic mulch.
Green Garlic
Another option is to not grow garlic for bulbs but to grow garlic to harvest in the green stage. Green garlic is harvested and sold like green onions. You can plant smaller cloves, cloves that have not been cold treated, or bulbils (the mini onion bulbs collected from scapes). Close spacings are used and plastic mulch is not necessary.
Green garlic is harvested like green onions and can be produced from smaller cloves, cloves that have not been cold treated or bulbils.